1. Field of the Invention
The present invention relates to a cage stop height readjusting apparatus for an elevator system and a method thereof, and in particular to an improved cage stop height readjusting apparatus for an elevator system and a method thereof which are capable of accurately stopping a cage or an elevator car at a predetermined floor at a zero level of a cage stop height.
2. Description of the Background Art
Generally, in a conventional elevator system, a sensor connected with a shaft of a cage driving motor generates output pulses proportionally to the RPM of the motor. These output pulses from a rotary encoder are accumulatively summed in accordance with a running direction of the cage, thereby recognizing a synchronous position of the cage.
Therefore, when initially installing an elevator, the height of each floor is measured and stored using the number of output pulses from the rotary encoder based on the position of a reference position (for example, the bottom of the lowest floor of a building). The cage is moved to the floor at which a cage call is generated based on the measured value. At this time, the position in which the bottom of the cage coincides with the height of the floor is called the zero level.
When the cage arrives at the destination floor, the cage often reaches the designated floor at a certain distance away from the zero level due to the erroneous operation of a control apparatus or the characteristics of various sensors. In addition, after the cage arrives, when the load of the cage is varied due to the loading or unloading of the passenger, the elongation of a wire connected with the cage is varied, so that the cage stops at a certain distance short of or over the zero level of the designated floor.
As a result, there may occur a problem such as a passenger getting-on and getting-ff problem due to the difference in height between the height of the desired floor and the height of the bottom of the cage both measured from a set reference position. Therefore, it is required to urgently adjust the stop height of the cage based on the zero level. At this time, the cage has to be re-driven to accurately adjust-the cage stop height. This operation is called a cage stop height readjusting operation.
FIG. 1 illustrates a schematic block diagram illustrating a conventional position control apparatus for a conventional elevator, as disclosed in U.S. Pat. No. 4,719,994 issued on Jan. 19, 1988, which is hereby incorporated by reference. This control apparatus includes a motor 4 for generating a driving force and transferring the force to a sheave 3 for running a cage 1, a speed detection rotary encoder 5 connected with a driving shaft of the motor 4 for outputting a speed signal V.sub.T which is proportional to the RPM of the motor 4, a speed reference signal generator 6 for receiving position detection signals LU, LD and RL from the position detector 1a, 1b, 1c of the cage 1 and generating a speed reference signal V.sub.P for a cage stop height readjusting operation, a subtractor 7 for performing a subtraction operation between a speed signal V.sub.T from the speed detection rotary encoder 5 and a speed reference signal V.sub.P from the reference signal generator 6 and outputting a deviation V.sub.E, and a speed control apparatus 8 for controlling the RPM of the motor 4 based on the deviation V.sub.E from the subtractor 7. In the drawings, reference numeral 2 denotes a balance weight.
In addition, the reference speed generator 6 as shown in FIG. 2 includes an input unit 6A for receiving the position detection signals LU, LD and RL, a CPU 6D for processing the position detection signals LU, LD and RL inputted through a ROM 6C, RAM 6B, the input unit 6A and the bus and outputting a reference speed signal V.sub.P, a timer 6E for generating a timing signal for an interrupt control, and an output unit 6F for outputting the reference speed signal V.sub.P computed.
The operation of the conventional elevator position control apparatus in FIG. 1 will be explained.
When the cage 1 arrives at the destination floor, the position detectors 1a , 1b, 1c installed on the cage 1 contact the position cam installed on each of the floors, and the position detector signals LU, LD and RL are transmitted to the reference speed generator 6 from the position detectors 1a, 1b, 1c.
FIGS. 3A-3C illustrate operational ranges of the position detection signals LU, LD and RL.
ARL is the cage stop height readjusting zone range, which is composed of the zone A which indicates that the cage stop height readjusting operation is needed in the up-travel direction, the zone B which indicates the normal stop height range, and the zone C which indicates that the cage stop height readjusting operation, is needed in the down-travel direction. Here, the zero point denotes the actual level of the floor.
Therefore, the CPU 6D of the reference speed generator 6 receives the position detection signals LU, LD and RL through the input unit 6A and the bus BUS, executes the program stored in the ROM 6C, and transmits the reference speed signal V.sub.P through the output unit 6F for the cage stop readjusting operation.
FIG. 4 illustrates the patterns of the reference speed signal V.sub.P and the speed signal V.sub.T of the cage 1 for the cage stop height readjusting operation.
In the zone A, the reference speed signal V.sub.P is increased by .DELTA.V step-by-step as shown in FIG. 4B for increasing the riding-on feeling of the cage, and at the speed V.sub.RL, for a determined time, the above-described state is maintained. Thereafter, when the cage comes into the zone B of the normal stop height, the reference speed signal V.sub.P becomes 0.
As a result, the speed control apparatus 8 receives the reference speed signal V.sub.P through the subtractor 7, thus driving the motor 4. In the zone A, the cage 1 is moved in the up-travel direction. As shown in FIG. 4, when the reference speed signal V.sub.P becomes 0, the speed signal V.sub.T is gradually decreased and then becomes 0. Therefore, the cage 1 arrives at the zero level.
The cage stop height readjusting operation will now be explained with reference to FIGS. 5 through 8.
When the power is supplied, the program read from the ROM 6C is executed, the reference speed generator 6 is initialized, the timer 6E is driven, and an interrupt signal is inputted.
When the interrupt signal is inputted from the timer 6E, the CPU 6D performs a processing routine for detecting the stop position of the cage 1 as shown in FIG. 5.
Namely, when the interrupt signal is inputted from the timer 6E, the CPU 6D judges whether the cage 1 is running in Step S1. As a result of the judgment, if the cage 1 is running, the flag FLAG is set to 0 in Step S7. If the cage 1 is stopped, it is checked whether the position detection signal RL, namely, the ARL, is at a high level in the zone A in Step S2.
As a result of the checking step, if the ARL is at a high level, the CPU 6D checks the level of the position detection signal LU or the position detection signal LU in the zone A, and thereafter it determines where the cage 1 is stopped among the zones A, B and C in Steps S3 and S4.
If the position detection signal LU is detected to be at a low level in the zone A, the CPU 6D outputs an up movement instruction to the speed control apparatus 8 through the output unit 6F. If the position detection signal LU is at a high level and the position detection signal LD is at a low level in the zone C, the CPU 6D outputs the down movement instruction to the speed control apparatus 8 through the output unit 6F. Thereafter, the flag FLAG is set to 1 in Steps S5, S6 and S8.
In the zone B, the position detection signals LU and LD are all at high levels. If the cage 1 is stopped in the normal zone B in which the cage stop height readjusting operation is not needed, the flag FLAG is set to 0 in Step S7. At this time, the flag FLAG denotes whether the reference speed signal V.sub.P is computed for the cage stop height readjusting operation.
When the processing routine for detecting the stop position of the cage 1 is finished, the CPU 6D checks the flag FLAG. If the flag FLAG is set to 1, the computation processing routine of the reference speed signal V.sub.P as shown in FIG. 6 is performed for the cage stop height readjusting operation.
Namely, if the flag FLAG is set to 1 in Step S9, the CPU 6D checks whether the position detection signals LU and LD are all at high levels in Step S10. As a result of the checking, if the position detection signals LU and LD are all at high levels, the reference speed signal V.sub.P is set to 0 in Step S11.
As a result of the checking, if the position detection signals LU and LD are not all at high levels, the CPU 6D compares the reference speed signal V.sub.P with a constant speed V.sub.RL in Step S12. If the speed V.sub.RL is not higher than the reference speed signal V.sub.P, the reference speed signal V.sub.P is set to the V.sub.RL in Step S14 so that the cage 1 is accurately stopped in the normal zone B. If the speed V.sub.RL is higher than the reference speed signal V.sub.P, the reference speed signal is set to the current reference speed signal V.sub.P plus an increase .DELTA.V in Step S13.
In addition, FIGS. 7 and 9 illustrate other examples of the patterns between the reference speed signal V.sub.P and the speed signal V.sub.T of the cage 1 for the cage stop height readjusting operation in the conventional art.
FIG. 7 illustrates a pattern when the cage 1 is stopped in the normal zone B. At this time, since the cage 1 moves into the normal zone B before the reference speed signal V.sub.P reaches the speed signal V.sub.T of the cage 1, the reference speed signal V.sub.P becomes 0.
Therefore, even when the cage stop height readjusting operation is finished, the distance L which is a distance from the zero level is increased compared to the distance as shown in FIG. 4.
In addition, FIG. 8 illustrates a pattern for overcoming the problems which occur in the example of FIG. 7. As shown therein, when the cage 1 is moving, the reference speed signal V.sub.P is increased up to V.sub.M, and then the same is slightly decreased down to a predetermined speed V.sub.RL. As a result, since the reference speed signal V.sub.P of the cage 1 is quickly increased and is larger than the pattern shown in FIG. 7, it is possible to shorten the distance L which is at a certain distance from the zero level.
Namely, if the flag FLAG is set to 1, the CPU 6D checks whether the position detection signals LU and LD are all at high levels in Steps S15 and S16. As a result, if the position detection signals LU and LD are all at high levels, the reference speed signal V.sub.P is set to 0, and the flag STA is set to 0 in Steps S17 and S18 for the cage stop height readjusting operation.
If the position detection signals LU and LD are all at low levels, it is checked in Step S19 whether the flag STA is set to 0. As a result, if the flag STA is set to 0, the CPU 6D sets the reference speed signal V.sub.P to a certain speed V.sub.M in Step S20. In addition, the flag STA is set to 1 in Step S21. At this time, V.sub.M becomes two or three times the V.sub.RL.
If the flag STA is not set to 0, the CPU 6D compares the reference speed signal V.sub.P with the speed V.sub.RL in Step S22. If the speed V.sub.RL is larger than the reference speed signal V.sub.P, the reference speed signal V.sub.P is set to V.sub.P +.DELTA.V in Step S23, and if the speed V.sub.RL is smaller than the reference speed signal V.sub.P, the reference speed signal V.sub.P is set to V.sub.RL in Step S24. Thereafter, the cage 1 is accurately stopped in the normal zone B.
Therefore, when the cage 1 is stopped in the normal zone B, since the cage 1 is re-driven using the reference speed signal V.sub.P, it is possible to shorten the distance L which is a certain distance from the zero level.
However, even when the cage stop height readjusting technique as shown in FIGS. 8 and 9 is used, in the conventional art since the cage 1 stops at a distance L from the zero level, there is a big problem for accurately stopping the cage at the zero level.